Conversion of hydrocarbon oil



' principally dehydrogenation reactions.

Patented May 2, 1944 2,347,648 CONVERSION OF HYDROCARBON OIL Charles L. Thomas Ill., assignors to Universal 111., a corporation of Delaware pany, Chicago,

and Edward C. Lee, Chicago,

Oil Products Com- No Drawing. Application November 30, 1938, Serial No. 243,261

18 Claims. (o 196-52) This invention relates to the conversion of hydrocarbons such as petroleum fractions and hydrocarbonaceous oils generally including synthetic oils from numerous carbon-containing sources. More particularly, the conversion involves hydrocarbons which may be vaporized without substantial decomposition.

More specifically the present invention involves conversion of hydrocarbons in the presence of specific types of catalytic materials which function to selectively promote the formation of very high antiknock gasoline. The preferred catalysts are prepared synthetically by definite steps of procedure which are specific in the production of catalysts of high activity for prolonged use.

The art of pyrolytically cracking and reforming hydrocarbons to produce high antiknock gasoline is very extensive and it is recognized that most of the basic principles involved are known and that particular commercial processes have been developed which embody these principles. On the other hand, where cracking and reforming of hydrocarbons are carried out catalytically, knowledge as to the application of catalysts is largely upon the same basis as it is in other catalytic fields, that is, it is largely em pirical. A large number of catalysts tried out in cracking and reforming operations accelerate reactions leading to the formation of gas rather than of high antiknock gasoline predominantly, this being particularly evidenced by reduced metal catalysts such as iron or nickel and also certain metal oxide catalysts which accelerate The reduced metal catalysts, in particular, have the disadvantage of being sensitive to sulfur poisoning and are quickly coated with carbonaceous materials which render them practically inert. This deposition of carbonaceous materials is frequently related to the type of decomposition selectively accelerated by the catalyst.

The present invention is concerned with converting hydrocarbon fractions in the presence of catalytic materials which are specifically adapted to accelerate the conversion of petroleum fractions and other hydrocarbonaceous materials so as to produce large yields of high antiknock gasoline boiling range fractions together with gaseous byproducts which contain unusually high percentages of readily polymerizable olefins useful in further increasing the gasoline yields The preferred catalysts for the process are characterized by selectivity in accelerating gasoline forming reactions rather than light-gas-forming reactions, by their selectivity in producing high antiknock gasoline, by their refractory character which enables them to retain their catalytic properties over extended periods of time under high temperature conditions of use and regeneration, by their ease and simplicity of manufacture and their exact reproducibility.

In one specific embodiment the present invention comprises subjecting petroleum fractions at elevated temperatures and at atmospheric or relatively low superatmospheric pressures to contact with catalytic materials comprising synthetically prepared composite masses of silica (S102), alumina (A1203), and zirconia. (ZlOz), producing concurrently relatively high yields high antiknock gasoline and gas containing rela tively high percentages of readily polymerizable olefins.

According to the present invention hydrocarbon fractions, for-example, a petroleum gas oil or a straight-run gasoline may be.pro'cessed at temperatures of the usual high pressure pyrolytlc cracking range but at substantially lower pressures while in contact with silica-alumina-zirconia catalysts. These catalysts may be prepared by a number of alternative methods which have certain necessary features in common as will i be subsequently described. Generally speaking, however, the catalysts may be considered to comprise an intimate molecular admixture of silica, alumina and zirconia, all of the components of which indicate more or less low activity individually but in the aggregate display high activity. The activity is not an additive function, it being relatively constant for a wide range of proportions of the components whether in molecular or fractions of molecular proportions. No one component can be determined as the one component for which the remaining components may be considered as the promoters according to conventional terminology, nor can any component be determined as the support and the others the catalyst proper.

According to one general method of preparation used before drying treatment, the preferred catalyst may be prepared by precipitating silica from a solution as a gel and subsequently admixing or depositing the alumina and zirconia upon the hydrated silica. One of the more convenient methods of preparing the silica gel is to acidify an aqueous solution of sodium silicate by the addition of an acid such as hydrochloric acid, for example. The excess acid and the concentration of the solution in which the precipitation is brought about determine in some measure the suitability of the silica hydrogel for subsequent deposition of alumina and zirconia. In general, suitable hydrated silica may be produced by the use of dilute solutions of sodium silicate and the addition of a moderate excess of acid whereby the desired active silica gel is obtained and conditions of filtering and washing are at an optimum.

After precipitating the silica it is treated and washed to substantially remove alkali metal ions. It is not known whether the alkali metal ions such as sodium ions are present in the primary gel in chemical combination or in an adsorbed state but it has been definitely determined that their removal is necessary if catalysts suitable for prolonged use in accelerating hydrocarbon conversion reactions are to be obtained. It is possible that the presence of the alkali metal impurities causes a sintering or fusion of the surfaces of the catalyst at elevated temperatures so that the porosity is much reduced with corresponding reduction in effective surface. 'Alkali metal ions may be removed by treating with solutions of acidic materials, ammonium salts generally, or salts of multivalent metals, more preferably those of aluminum and zirconium. When treating with acids, as for example, with hydrochloric acid, the acid extracts the alkali metal impurities in the silica gel. The salts formed and acid are then substantially removed by water washing treatment. Where ammonium salts or salts of multivalent metals are used, the ammonium or multivalent metals apparently displace the alkali metal impurities present in the composite and the alkali,metal salts formed, together with the major portion of the multivalent salts, are removed in the water washing treatment. Some of the multivalent metals introduced into the silica hydrogel in the purifying treatment may become a permanent part of the composite, whereas, in the treatment with ammonium salts small amounts of the ammonium salts remaining after the washing process will be driven oil? in subsequent treatment at elevated temperatures.

In one of the preferred methods of compositing the hydrated materials, the purified precipitated hydrated silica gel may be suspended in a solution of zirconium and aluminum salts in the desired proportions and zirconia and alumina deposited upon the suspended silica by the addition of volatile basic precipitants such as ammonium hydroxide, for example, or ammonium carbonate, ammonium hydrosulfide,ammonium sulfide or other volatile basic precipitants such as organic bases may be employed. According to this method, the purified silica gel may be suspended in a solution of zirconium and aluminum chlorides, for example, and the hydrated zirconia and.hydrated alumina precipitated by the addition of ammonium hydroxide. In this example, the alumina, and zirconia were copreoipitated. Good results maybe obtained by depositing one of these components prior to the remaining component.

Alternately the purified hydrated silica gel may be mixed while in the wet condition with sepa: rately prepared hydrated alumina and hydrated zirconia precipitated either separately or concurrently as for example by the addition of volatile basic precipitants to solutions of salts of aluminum and zirconium. The hydrated alumina and hydrated zirconia thus prepared are substantially free from alkali metal ions and can be admixed with the purified silica gel. However, if alkali metal ions are incorporated as when the hydrated alumina is prepared from sodium aluminate, for example, or if zirconium tetrahydroxide is precipitated by the inter-action of zirconium sulfate and alkali metal cyanides, or the inter-action of zirconium sulfate and sodium acetate or sodium hydroxide, regulated purification treatment and water washing by methods selected from those described in. connection with the purification of the hydrated silica gel to remove alkali metal ions would be required. Care should be observed in the selecaeizeis of the aluminum and zirconium salts.

In the methods above described a silica hydrogel free from alkali metal ions was admixed or had deposited thereon relatively pure hydrated alumina and hydrated zirconia prior to drying treatment. In methods described below the hydrated silica, hydrated alumina and hydrated zirconia are concurrently precipitated or admixed, and treatment to remove alkali metal ions applied to the composited material prior to drying treatment either in the presence of the original reactants or subsequent to water washing. Thus, solutions of silicon compounds more usually alkali metal silicates and soluble aluminum and zirconium salts may be mixed under regulated conditions of acidity or basicity to .jointly precipitate hydrated silica, hydrated alumina and hydrated zirconia in varying proportions. For example, solutions of sodium silicate, aluminum chloride and zirconyl chloride may be mixed and alkaline or acid reagents added according to the proportions used so that a pH of 3-10 is obtained. In cases where a sol is formed the precipitation may be brought about by addition of a volatile base as for example ammonium hydroxide, and alkali metal salts removed by water washing, or the composite may be treated as indicated above in connection with the purification of the hydrated silica to remove alkali metal ions. Various methods are possible for the preparation 01 the hydrated silica, hydrated alumina and hydrated zirconia separately or in combination and the purifying treatment is necessary where alkali metal ions are present in substantial amounts.

The character and efllciency of the ultimately prepared silica-alumina-zirconia catalyst will vary more or less with precipitation and/or mixing, purification treatment, ratio of components, calcining, etc,, several specific examples being given. The ratio of the components may be varied within wide limits, the limiting factor being more in evidence with respect to small proportions than with larger proportions of the various components. In general, it appears that two to six mol per cent of alumina and zirconia together with reference to silica may be considered an approximation of the minimum proportions. Experience has indicated superior results as to yields and octane number of gasoline product for catalysts comprising silica, alumina and zirconia as compared with silica-alumina or silica-zirconia catalysts. It has also been observed for some charging stocks that as the amount of zirconia is increased in a catalyst composite the dehydrogenating reactions are increased so that the gases evolved contain larger percentages of hydrogen. Further, the zirconia containing catalysts seem to be more stable to high temperature regeneration than the silica-alumina catalysts.

After the alumina and zirconia have been mixedv with, or deposited upon the purified hydrated silica gel and water washed if desired, as

described for one general method of preparation, or after the hydrated silica, hydrated alumina and hydrated zirconia have been composited and treated to remove alkali metal ions, as described for another general method of preparation, the catalytic material may be recovered as a filter cake and dried at a temperature of the order of 240-300 F. more or less, after which it may be formed into particles of a suitable definite size ranging from powder to various formed sizes obtained by pressing and sizing or otherwise formed into desired shapes by compression or extrusion methods.

By calcining at temperatures of the order of approximately 850-1000 F., or higher, maximum activity of the catalyst is obtained and a further dehydration occurs so that for example after a considerable period of heating at 900 F., the water content as determined by analysis is of the order of 2-3% which is firmly fixed and does not appreciably vary either as the result of long service or a large number of reactivations at considerably higher .temperatures.

Catalysts prepared by the various types of procedures outlined evidently possess a large total contact surface corresponding to a desirable porosity, the pores of the catalyst particles being of such size and shape that they do not become clogged with carbonaceous deposits after a long period of service, and are therefore not difilcult to reactivate by oxidation. This structure is also retained after many alternate periods of use and reactivation as evidenced by the fact that the catalysts may be repeatedly reactivated by passing air, or other oxidizing gas, over the spent particles to burn off deposits of carbonaceous material at temperatures above 800 F., temperatures as high as 1400-1600 F. having been reached without apparently affecting the catalytic actlvity.

In accordance with the present invention the catalysts may be conveniently utilized in cracking and reforming reactions as for example when employed as filling material in tubes or chambers in the form of small pellets or granules. In cases wherein hydrocarbon fractions readily vaporizable at moderate temperatures without extensive decomposition are employed, the average particle size may be within the approximate range of 1-10 mesh, which may apply either to pellets of uniform size and short cylindrical shapes, or to particles of irregular size and shape produced by the grinding, consolidating and sizing of the partially dehydrated materials. While the simple method of preheating a given fraction of hydrocarbon oil vapors to a temperature suitable for their cracking in contact with the catalysts and then passing the vapors over a stationary mass of catalyst particles may be employed in some cases, it may be preferable to pass the preheated vapors through banks of relatively small diameter catalystcontaining tubes in multiple connection between headers, since this arrangement of apparatus is better adapted to per mit exterior heating of the catalyst tubes to compensate for the 'heat absorbed in the endothermic cracking reactions and to dissipate heat in the regeneration.

After the passage of the oil vapors over the catalyst, the products may be separated into material unsuitable for further cracking, intermediate insufliciently converted fractions amenable to further catalytic cracking, gasoline boiling range materials, and gases, the intermediate fracthe charging stock so that ultimately there is complete recycling of all fractions and maximum utilization of the charging stock for gasoline production. As an alternative mode of operation the catalyst may be suspended in a stream of oil as a powder and treated under suitable conditions of temperature, pressure and contact time.

The-charging stock may comprise hydrocarbon fractions which are vaporizable without substantial decomposition, heavier hydrocarbonaceous materials which are not readily vaporized or generally, the high boiling as well as lower boiling fractions. It should be recognized that hydrocarbon mixtures of low antiknock value such as naphtha cuts. gasoline lacking in light and/or heavy ends, cracked gasoline, synthetic products, etc., may be processed according to the present invention.

The normally gaseous fraction separated from the gasoline. product contains much larger proportions of readily polymerizable olefins, more particularly propene and butenes, than are usually experienced in ordinary thermal cracking and these may be readily polymerized using ther mal and/or catalytic treatment to produce additional yields of gasoline which may be blended if desired with the major gasoline product produced in the process. A number of polymerizing catalysts are generally known, particularly phosphoric acid deposited on siliceous adsorbent, and this and/or other polymerizing catalysts may be used to polymerize the above mentioned olefins.

The application of the present invention to cracking and reforming of hydrocarbon fractions besides being characterized by the presence of novel catalysts is further characterized by the moderate operating conditions of temperature and pressure. Temperatures employed in contact with the catalysts may be within the range of 800 to 1200 F. Substantially atmospheric pressure or moderate superatmospheric pressure up to pounds per square inch or more may be used. such pressures being somewhat governed by flow conditions through the vaporizing and conversion zones and the subsequent fractionating and collecting equipment.

The following specific examples are given to illustrate the process of the invention, the methods of catalyst preparation also being given. The process should not be considered as limited to these examples or to the particular catalyst preparations, these being given as illustrative of the novelty and utility of the invention.

A catalyst prepared according to the present invention consists of approximately 111015 of silica (SiO2), 2 mols of alumina (A1203), and 4 mols of zirconia (ZIOz). The general procedure observed in preparing this catalyst was to precipitate silica gel, wash and treat to free from alkali metal ions, suspend the purified precipitated silica in a solution of aluminum chloride and zirconyl nitrate and precipitate alumina and zirconia in the presence of the suspended silica by the use of ammonium hydroxide.

1200 cc. of the commercial grade of sodium silicate was diluted with 12 liters of water. dilute solution of hydrochloric acid was also prepared by diluting 420 cc. of concentrated (l2 tions being returned directly to admixture with re normal) hydrochloric acid with 1580 cc. of water. 1600 cc. of the dilute hydrochloric acid was gradually added to the diluted sodium silicate which was then further diluted by the addition of 3 liters of water. An additional 300 cc. of the dilute acid was finally added after which the precipitated silica gel was collected on a filter. The

silica gel was then slurried in 10 liters of water and again filtered, this operation being repeated several times. Subsequently the washed silica gel was treated to remove alkali metal ions still remaining as impurities in the silica gel by fur ther treatment with dilute hydrochloric acid, the silica gel being slurried in 10 liters of water containing 45 cc. of the concentrated acid, the treatment being repeated twice. The precipitate was then subsequently washed several times until substantially chloride-free. 913 parts by weight corresponding to 1.86 mols of the purified silica hydrogel was suspended in 2500 parts by weight of water, 20.4 parts by weight (0.0744 mols) of zirconium nitrate and 18 parts by weight (0.0744 mols) of aluminum chloride was dissolved in 500 parts by weight of water. The solution of mixed zirconium and aluminum salts was added to the suspension of the slica hydro-gel and thoroughly agitated whereupon a solution of 472 parts by weight of normal ammonium hydroxide solution was added to effect the precipitation of hydrated alumina and hydrated zirconia. The composite precipitate was then filtered, water washed and dried at approximately 300 F. The dried material was then pressed and broken up to obtain particles of approximately 6-10 mesh and the 6-10 mesh product calcined at approximately 900 F.

The catalyst was placed in a vertical cylindrical chamber and vapors of a Pennsylvania gas oil preheated to a temperature of 932 F. directed downward through the catalytic material in a single pass. The gasoline, gas and unconverted material were separated. The following tabulation is a summary of the results obtained on 3 runs with the catalytic material, the catalyst being regenerated between runs by the use of an oxygen-containing gas.

I Run #1 I Run #2 Run #3 l Gasoline 400 F., E. P.: i I

Volume per cent oi charge U; 29. 1 29. 4 29. 5 A. P. I.@60F 60.1 I 59.9 59,6 Octane number, motor method: 79. a 78.9 78.8 Reid vapor pressure, lbs y 8 8 8 Englcr distillation: I

I. B. 89 97 95 122 129 129 143 147 152 162 166 1b9 213 214 214 2E4 284 278 353I 352 351 E. P., F s99 401 400 Gases (boiling range below +l I (3.): Weight per cent of charge 10.5 7 6 7.8

Polymerizable gas corresponding to I propcne and hutene content:

Weight per cent charge l l l (i. 5. 0 5.1 Gas oil recovered (recycle stock):

Volume per cent of charge 67. 8 68. 2 68.1

.-\. l. l. 60 F 37.2 I 37.4 37.4

Various preparations made containing varied proportions of silica, alumina and zirconia were prepared, as for example, 100 SiO2I4A12O3Z8ZrO2, 100 SiOaGAlZOwlZrOZ, 100 SiO2:2AlzOs:12ZrO2, and similar results were obtained.

Duplicate runs using quartz chips in place of the catalyst when processing gas oil give a yield of less than 4% gasoline. I

We claim as our invention:

1. A conversion process which comprises subjecting hydrocarbon oil at cracking temperature to the action of a calcined mixture of the hydrogels of silica. alumina and zirconia.

2. A conversion process which comprises subjecting hydrocarbon oil at cracking temperature to the action of a calcined mixture of precipitated silica, alumina and zirconia.

3. A conversion process which comprises subjecting hydrocarbon oil at cracking temperature to the action of a calcined mixture of a major proportion of precipitated silica and minor proportions of precipitated alumina and zirconia.

4. A process for producing gasoline which comprises subjecting hydrocarbon oil heavier than gasoline to cracking conditions in the presence of a calcined mixture of the hydrogels of silica, alumina and zirconia. i

5. A process for producing gasoline which comprises subjecting hydrocarbon oil heavier than gasoline to cracking conditions in the presence of a calcined mixture of precipitated silica, alumina and zirconia.

6. A process for producing anti-knock motor fuel which comprises subjecting hydrocarbon oil containing gasoline fractions to cracking conditions in the presence of a major proportion of precipitated silica and minor proportions of precipitated alumina and zirconia.

7. A process for producing anti-knock motor fuel which comprises subjecting hydrocarbon oil containing gasoline fractions to cracking conditions in the presence of a calcined mixture of precipitated silica, alumina and zirconia.

8. A hydrocarbon oil cracking catalyst comprising a calcined mixture of the hydrogels of silica, alumina and zirconia.

9. A conversion process which comprises subjecting hydrocarbon oil at a temperature in the range of about 800 F. to about 1200 F. to the action of a calcined mixture of the hydrogels of silica, alumina and zirconia.

10. A conversion process which comprises subjecting hydrocarbon oil at a temperature in the range of about 800 F. to about 1200 F. to the action of a calcined mixture of precipitated silica, alumina and zirconia.

11. A process for producing gasoline which comprises subjecting hydrocarbon oil heavier than gasoline to a temperature in the range of about 800 F. to about 1200 F. in the presence of a calcined mixture of the hydrogels of silica, alumina and zirconia.

12. A process for producing gasoline which comprises subjecting hydrocarbon oil heavier than gasoline to a temperature in the range of about 800 F. to about 1200 F. in the presence of a calcined mixture of precipitated silica, alumina and zirconia.

13. A process for producing anti-knock motor fuel which comprises subjecting hydrocarbon oil containing gasoline fractions to the action of a calcined mixture of the hydrogels of silica, alumina and zirconia at a temperature in the range of about 800 F. to about 1200 F.

14. A hydrocarbon conversion catalyst comprising a calcined mixture of the hydrogels of silica, alumina and zirconia., the silica being in major proportion and the alumina and zirconia being in minor proportions.

15. A process for reforming straight-run gasoline which comprises subjecting said gasoline at a temperature in the range of about 800 F. to about 1200 F. to the action of a calcined mixture of precipitated silica, alumina and zrconia.

16. A process for improving cracked gasoline which comprises subjecting said gasoline at a temperature in. the range of about 800 F. to about 1200 F. to the action of a calcined mixture of precipitated silica, alumina and zirconia.

CHARLES L. THOMAS. EDWARD 0. LEE. 

